CD-R AND DVD MEDIA

Are your pictures still on your disc?

  
BACK UP!!! BACK UP!!! BACK UP!!!
Copying your pictures onto CD or even DVD's  is inexpensive. It is a quick and good way of keeping all your computer files and pictures backed up and in another location. There are a few pitfalls to avoid with these discs. The following information might be a an eye opener for some, but I will try to explain without getting to technical. CD's Hold 650-800mb of data (about 240 x 6mb pictures) DVD's are 4.7gb (4,700mb) and will hold about  1,500 6mb pictures. (All these are Jpeg images and approximate capacities.) There are dual layer DVD's out now, but are not to be recommended for the purpose of backing up pictures. The dual layer discs are expensive and they have some compatibility issues.

HARDWARE NEEDED

Most Computers come with at least a CDRW (cd disc writer and player). Some come with a DVD writer now days. If you have neither, I would recommend getting a USB EXTERNAL CD/DVD writer. I brought a high speed external cd/dvd writer for less the $100. Benefit of an external unit is I can move it from PC to PC. They come with different read/write speeds. You could say they are all measured against a normal Music CD time of 1 hour. so a 4x CD writer will write a full CD in about 15minutes. . We are only really interested in the write speeds.  52X write speed for Cd-r's and 16x write speed for DVD's is the top speeds found on units as I write this article. Remember this is WRITE speed. most  units will READ all discs very fast

NOTE: The blank discs come marked with their speed capabilities. if those cd-r's are marked 16x they will not write at 48x but only 16x or slower on your writer. Most CD-r's nowdays are high speed 48x etc Sometimes the blank discs will not write at a slower speeds than their rated speed. Check before buying discs if you have an older drive, this is especially relevant to DVD's

CD-R and CD-RW DISCS
CD-R discs are write once only discs. and CD-RW you can write over and over again. For the purpose of archiving pictures, CD-RW are not to be considered. They do not last as long and they have a few compatibility problems with the different manufacturers ideas of how to recorded to them. So we will only consider CD-R discs (write once discs) from now on. Blank CD'R's are much cheaper than there bigger brothers, DVD's

CD-R's  hold from 650mb to 700mb of data depending on discs. That's about 150  6mb high quality pictures. For optimum archival purposes set your burner up to use the 650mb size when writing to the discs (if possible). The recording system used at 650mb is closer to the true CD standard giving maximum compatibility. also always burn CD-R's below the manufacturers stated top speed.

Do not use discs marked "music discs" The only difference between these expensive discs and the normal discs is you are donating a small sum too the music industry. Didn't know that did you!!!

Construction of CD-R's and normal CD's is shown below:

            Construction of CD-R

Construction of normal (music and software CD)
Study the different construction methods used to make CD's. The laser reads through the bottom surface of the disc (the side we always worry about scratching). You will see that ordinary CD's (right) have a plastic layer  between the data layer/reflective layer and label surface. But look at the the CD-R(left). We have 3 very thin layers laid onto the just one piece of plastic. The data/reflective layer is just below the label. Your data is just below that label. Press to hard with that sharpie!!!  Use cheap  labels and they can peel off taking the data layer with it.  Over time  some solvents from pens and labels will work there way down and oxidize the reflective layer as well!! Oxidized silver reflective layers is the most common cause of CD failures. 

So how do I avoid these problems? Some manufactures make a point of silk screening tough layers to help protect these data layers below.  Promaster/delkin gold disc being one type. There are special pens ("xylene-free" marker pens) for writing on the discs that avoid the bleed through problem. As to the many different types of CD labels, the jury's still out. It goes without saying that if the label peels off it will take your data layer with it!!

Just treat the label side of your CD-r's with respect from now on. and write on them using the right pens.

Before moving on to the subject of how long they CD-R will last, any discs manufactured with GOLD instead of silver reflective layers, will not suffer from oxidization and is a a good pointer towards a good archival discs. But gold is expensive. WARNING: Some manufacturers call their discs "gold discs", but this refers to the die/layer appearance only, not the materials used.

DVD DISCS

There are two main types of DVD discs out there DVD+R / DVD+RW and DVD-R/DVD-RW( sometimes called dvd ram).  Again I will stick my head on the block and state that the rewritable flavors, DVD-RW and DVD+RW discs are not to be recommended for archival purposes, which is the purpose of this article. DVD-RW are totally incompatible with nearly all standard DVD players. So we will again stick to the DVD-R and DVD+R (write once only discs).

DVD's are 4.7gb (4,700mb) and will hold about  1,500 6mb pictures. There are dual layer DVD's out now, but are not to be recommended for the purpose of backing up pictures. The dual layer discs are expensive and they have some compatibility issues

Surprise, Surprise, there are two flavors of DVD"S   -r and +r discs and recorders. Same old story of two entrenched camps of manufacturers (This is again going to be repeated soon with the new DVD standard coming DVDHD and Blue ray camps). Ok, so I admit I had a Betamax machine as well.

Some hardware now will record both types of discs DVD-R and DVD+r. "Hurray". But check your recorder and only use the types of discs for your recorder (either DVD-R or DVD+R).

TIP: If you are making DVD movies or still pictures shows to view on a standard DVD player on your TV, DVD+R is the nearest to the book standard for DVD. But you will find most modern DVD players will play both the recordable once only DVD-R and DVD+r  discs well.

Most Recordable DVD have a plastic protective layer added below the label like a normal CD, so do not suffer from some of the problems of labels and scratching mentioned in the previously above.  Except to point out that some solvents from the wrong pens and labels can still damage the reflective layer by bleed to the reflective layer over time. But again you can buy Gold reflective layer DVD's at a price!

Personal note: Because of the tighter packing of data on DVD's they are less forgiving of scratches and faults. For a quick back up of lots of data, great. But to truly ARCHIVE your pictures I  stick to GOLD CD's

HOW LONG WILL MY DISCS LAST?

Taking aside the label side issues covered already.

All Recordable CD's and DVD's use a dye to record the data onto. This changes color when hit by a high powered laser, these changes are treated as 010101's, which is the only thing computers really understand anyway. (I got to count past one in 1st grade ;-). The dies used by the different manufacturers all have different properties. They are all affected by exposure to UV and light, so don't store your archive discs on the car seat! Keep them in a archival type album or the plastic cases. There is even talk of some of the plastic cases giving off harmful gases which effect the discs

NOTE: All those millions developing CD's and they still can't make a plastic case that does not break when you look at it).

Now to the dies used to record your data. The problem here is that manufacturers don't normally tell you what dies are used, and we can't tell sometimes because the reflective layer alters the disc color as well. The many dies used in construction of the discs. The three main types being used (approximate color)

Metal-Cyanine (blue/green colour)

Metallized Azo (Blue)

Phthalocyanine (very light green) (BEST)

Most good manufacturers (Sony, TDK, Phillips, Promaster, Delkin etc) are using Phthalocyanine dye a lot. It is a very light green color with discs having the silver reflective layer.

Many things influence how long the discs will last, construction, materials used, conditions of storage etc.

Storage is the key. Just buy good brand discs and store them in a safe dry/cool dark place.

Always verify your disc is readable before you put it away.

For more in depth info I recommend visiting the nonprofit OFFICIAL STORAGE TECHNOLOGY ASSOCIATION Site.

I welcome any comments. Good and bad

Please excuse my "English"

   
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